1. Field of the Invention
The present invention relates to cooling the inside of a gantry having an X-ray tube and an X-ray detector in an X-ray computed tomographic apparatus (computer tomography (CT)).
2. Description of the Related Art
JP-A 2003-144425 proposes a method wherein elements in a rotor are partitioned by walls to separately control the atmospheric temperatures in the respective elements. However, a gantry housing is not substantially sealed off from the outside, and is not structured to be able to inhibit noise or exhaust heat into an examination room. This document describes in FIG. 4 the provision of an heat exchanger within the gantry housing, but does not describe any structure for obtaining an efficient cooling function.
JP-A 10-234721 proposes the structure of a gantry housing designed to prevent dust which may lead to decreased performance or a breakdown from being accumulated in a gantry. This structure has a double cover, but is not designed to guide the air in a gantry to another place, so that the gantry housing is not substantially sealed off from the outside.
An X-ray computed tomographic apparatus is capable of displaying, substantially in real time, tomograms or three-dimensional images of organs in a patient that are invisible to the naked eye. Such an X-ray computed tomographic apparatus is currently an essential medical instrument in the most advanced medical field where rapid and proper medical practices are needed. In order to meet the high clinical needs, further technological enhancement is being made, but, on the other hand, problems are occurring, such as noise produced by exhaust air from fans or heat released into the examination room. That is, if noise increases along with an increase in the amount of air from the exhaust fan for letting out a great amount of heat generated in the gantry, not only a conversation between a patient and a doctor may be prevented but also the patient may feel uneasy. Moreover, the amount of exhaust heat from an X-ray tube is already so great as to impose a high load on the air-conditioning equipment in the examination room. More exhaust heat restricts the place where the apparatus can be installed.
However, as the X-ray computed tomographic apparatus uses a technique for forming an image from X-ray detector signals obtained at a plurality of angles, the X-ray tube that generates a great amount of heat has to be installed inside the rotor. It is thus difficult to directly cool the X-ray tube alone. Therefore, according to a method generally used, exhaust heat from an X-ray tube cooler installed in the rotor is once released into a space between the rotor and the gantry housing, and then discharged to the examination room by the exhaust fan attached to the gantry housing. It is however difficult to inhibit the noise or the heat release into the examination room as long as the structure remains the same.